0355-design-twitter.js

/** 
 * https://leetcode.com/problems/design-twitter/
 * Your Twitter object will be instantiated and called as such:
 * var obj = new Twitter()
 * obj.postTweet(userId,tweetId)
 * var param_2 = obj.getNewsFeed(userId)
 * obj.follow(followerId,followeeId)
 * obj.unfollow(followerId,followeeId)
 */
 class Twitter {
    constructor () {
        this.tweets = [];
        this.following = new Map();
    }
    
    postTweet (userId, tweetId, { tweets } = this) {
        tweets.push({ authorId: userId, id: tweetId });
    }
    
    getNewsFeed (userId, newsIDs = [], { tweets, following } = this) {
        for (let i = (tweets.length - 1); ((0 <= i) && (newsIDs.length < 10)); i--) {
            const tweet = tweets[i];

            const isAuthor = tweet.authorId === userId
            const isFollowing = following?.get(userId)?.has(tweet.authorId);
            const canAddTweet = isAuthor || isFollowing
            if (canAddTweet) newsIDs.push(tweet.id);
        }

        return newsIDs;
    }
    
    follow (followerId, followeeId, { following } = this) {
        if (!following.has(followerId)) following.set(followerId, new Set());

        following.get(followerId).add(followeeId);
    }

    unfollow (followerId, followeeId, { following } = this) {
        if (following.has(followerId)) following.get(followerId).delete(followeeId);
    }
}